Powder bed fusion is an additive layering process by which pulverulent, in particular metallic and/or ceramic raw materials can be processed to three-dimensional work pieces of complex shapes. To that end, a raw material powder layer is applied onto a carrier and subjected to laser radiation in a site selective manner in dependence on the desired geometry of the work piece that is to be produced. The laser radiation penetrating into the powder layer causes heating and consequently melting or sintering of the raw material powder particles. Further raw material powder layers are then applied successively to the layer on the carrier that has already been subjected to laser treatment, until the work piece has the desired shape and size. Selective laser melting or laser sintering can be used in particular for the production of prototypes, tools, replacement parts or medical prostheses, such as, for example, dental or orthopaedic prostheses, on the basis of CAD data.
EP 2 859 973 A1 describes a powder processing arrangement for use in an apparatus for producing three-dimensional work pieces by selectively irradiating a raw material powder with electromagnetic or particle radiation, wherein a carrier element comprises a build section adapted to carry a raw material powder layer while being selectively irradiated with electromagnetic or particle radiation and at least one transfer section adapted to carry a raw material powder layer prior to being selectively irradiated with electromagnetic or particle radiation. A heating device is adapted to preheat the raw material powder carried by the transfer section of the carrier element prior to being applied to the build section of the carrier element so as to form the raw material powder layer to be selectively irradiated with electromagnetic or particle radiation.
Further, EP 2 878 409 A1 discloses a method and a device for controlling an irradiation system for use in an apparatus for producing a three-dimensional work piece and comprising a first and the second irradiation unit. A first and a second irradiation area are defined on a surface of the carrier adapted to receive a layer of raw material powder. A layer of raw material powder applied onto the carrier in the first irradiation area is irradiated by the first irradiation unit, wherein the operation of the first irradiation unit is controlled in such a manner that the raw material powder is preheated. Thereafter, the layer of raw material powder applied onto the carrier in the first irradiation area is irradiated by means of the second irradiation unit, wherein the operation of the second irradiation unit is controlled in such a manner that the raw material powder is heated to a temperature which allows sintering and/or melting of the raw material powder in order to generate a layer of the three-dimensional work piece. While the first irradiation unit irradiates a layer of raw material powder applied onto the carrier in the first irradiation area, a layer of raw material powder applied onto the carrier in the second irradiation area is irradiated by the second irradiation unit. Furthermore, while the first irradiation unit irradiates a layer of raw material powder applied onto the carrier in the second irradiation area, a layer of raw material powder applied onto the carrier in the first irradiation area is irradiated by the second irradiation unit.